Child and adolescent obesity is increasing at an alarming rate. Although the etiology of the overweight epidemic is complex, consumption of soda and other sweetened beverages has emerged as a significant dietary contributor. The proposed study will limit the availability of sweetened soda/beverages on high school campuses for a period of two school years and examine the effects on students' diet and weight patterns. Previous school-based interventions that have emphasized improving dietary behaviors through education have, for the most part, yielded disappointing results. This study, instead, will focus upon changing the school environment by eliminating sweetened soda/beverages from vending machines and other campus venues. The intervention will be conducted at two large ethnically mixed public high schools; two comparable high schools will serve as controls. Approximately 1200 9th grade students (600 from intervention schools and 600 from control schools) will be followed for 2 years. Primary study outcomes will be anthropometric variables (body mass index and percent body fat as determined by bioelectrical impedance), and dietary variables including consumption of soda and other sweetened beverages. Compensatory dietary changes by study individuals, as well as physical activity and television viewing, will be assessed. Effects of the intervention will be compared by gender, socioeconomic status, and race/ethnicity. Institutional barriers to intervention will be evaluated and guidelines for intervention replication will be developed.